The present invention relates to the sector of self-propelled handling or public works appliances equipped with at least one stabilizer, for example earthmoving appliances of the shovel-loader type, and more particularly to a safety device intended for equipping such appliances.
There are also certain types of self-propelled excavators on tires, using stabilizing devices (usually a pair at the front and/or at the rear, according to circumstances), to ensure good stabilization of the chassis by bringing the stabilizing devices to bear on the ground.
However, the sector with which the invention is particularly concerned is that of appliances of the shovel-loader type, although this must in no way be considered as a limitation of the subject of the invention.
Such appliances consist, in general terms, of a self-propelled central structure, on which are mounted a front assembly at the front and a hydraulic shovel assembly at the rear: the loader assembly comprising a large-size bucket is used for the loading of materials, whilst the fixed or laterally shiftable shovel assembly comprises a smaller bucket, the orifice of which is generally directed towards the shovel-loader, and is mainly used for digging trenches.
It goes without saying that the term "assembly" used in this description is to be understood in a very broad sense: depending on the particular types of use, there can be, at the front, a fork lift, a sweeper, a bulldozer blade or a snow plough and, at the rear, a pneumatic hammer or concrete-breaker, a rock-cutting tooth, an auger, a grab, a trapezoidal bucket, a ditch-cleaning bucket, a pruner or a tree-dozer.
In fact, with most of the assemblies located at the rear of such appliances, one or more stabilizers, of which the position relative to the ground is controlled by means of an associated lever, may be used.
In practice, at the rear there is a pair of stabilizers which, when brought in contact with the ground, make it possible to ensure the stability of the appliance by lifting the latter slightly in the region of its rear drive wheels. However, the invention is not limited to this common use, but also relates to appliances having four stabilizers with four drive wheels or having a single sliding stabilizer.
The structure of these stabilizers can vary (telescopic structures of the jack type, the rod of which ends in a bearing shoe, or articulated arms which are generally in an axis parallel to the longitudinal direction of the appliance and which likewise end in a bearing shoe). However, the function of these stabilizers remains essentially the same: to ensure the stability of the appliance during work carried out with the rear assembly, in particular a hydraulic shovel.
The rest of the description will mention the "lowering" and "raising" of the stabilizers, and this must be understood in a broad sense embracing the various possible types of structure. Likewise, reference will be made to an "earthmoving appliance" with a pair of stabilizers which are arranged at the rear of the appliance and of which the position relative to the ground is controlled from inside the cab by means of an associated lever: this hypothesis, although being the most common, is nevertheless in no way limiting.
When the driver of a shovel-loader wishes to use the rear assembly, particularly a hydraulic drag shovel, he rotates his seat through 180.degree. to gain access to the various control levers. In particular, the driver actuates the levers controlling the lowering of the stabilizers, until the desired lifting of the wheels is obtained; moreover, he may very probably act on either one of these levers in order to correct the sitting position on a cross slope.
This operation is of course carried out when the appliance is stationary, that is to say the driver has put the lever controlling the reverser of the direction of movement of the gear-change lever into neutral.
It is appropriate to note that transmissions of the hydromechanical type usually possess a movement reverser actuable without disengaging the clutch. Mention will be made, in this case, of a clutch reverser or movement reverser, reference sometimes being made to the term "power shift" used in the agricultural sector; moreover the transmission will often have a front clutch and a rear clutch, with a neutral position of the reverser, and the driver can put the reverser into the neutral position directly by associated valve means which are well known in this sector, means of the electromechanical type actuated directly by the said control lever, or any other equivalent means.
When the driver wishes to move the appliance, he has to raise the stabilizers until the said appliance rests on its wheels once again; he then rotates his chair once more in order to resume the driving position and then acts on the control lever of the reverser to change to forward movement or movement in reverse.
However, it can happen that, when the appliance is still resting on its stabilizers, the driver either inadvertently knocks the control lever of the reverser or has neglected to return the said lever to neutral after a checking operation.
In this case, as soon as the rear wheels of the appliance touch the ground, the machine moves in a way which the driver does not expect. He then has to react quickly to return the control lever to the neutral position, since the movement of the appliance can be a danger to the environment and, above all, to a person who may be knocked over by the machine or wedged between the loading bucket and a natural obstacle.
It can easily be appreciated that several seconds are required for the driver to become aware of this, then act to rotate his seat (which is often locked in the rear working position) and finally reach the control lever of the reverser or one of the safety devices usually provided (foot pedal and/or push-button located at the end of the control lever of the loader assembly), and this risks having consequences which are distressing and even dramatic in some cases.
Consequently, the manufacturers are now studying safety devices intended for equipping these appliances in order to eliminate the abovementioned risk.
One solution could involve purely and simply blocking the action of the control levers of the stabilizers when the reverser lever is not in the neutral position.
Such a device would have the advantage of simplicity, but in practice there would be disadvantages: in fact, the driver must first be aware that the lever or levers on which he acts have no effect on the stabilizers, he must then rotate his chair to reach the control lever of the reverser and finally he must return to the rear working position once again, in order to act on the control levers of the stabilizers. These operations are complicated for the driver and make him waste what may be valuable time.
The object of the invention is to provide a safety device capable of "cutting off" the transmission of the appliance automatically during the control of the raising of the stabilizers, when the control lever of the reverser or the equivalent control means used is not in neutral.
Another object of the invention is to provide a safety device making it possible to alert the driver when the transmission reverser has been returned to the neutral position without his knowledge, so that he can put the appliance back into operation under normal conditions.
Another object of the invention is to provide a safety device of a simple design which requires inexpensive actuating means and which is easy to install on an appliance on which the manufacturer had not provided anything for this purpose, at the same time even profiting from existing mechanical and/or electrical equipment.